Determination of Trace Phosphate in Water Samples by Spectrophotometry with Cloud Point Extraction

A novel separation and concentration system for determination of trace phosphate in water samples was established by spectrophotometry with the cloud point extraction(CPE) technique.The method used ammonium molybdate and ascorbic acid as chromogenic agents that was appled to detect the content of phosphorus by colorimetry of phosphomolybdenum blue,and potassium antimonyl tartrate as catalyzer in acidic medium.After formation steadily,the phosphomolybdenum blue was heated for 10 minutes by water bath at 80℃,and then separated from water phase by extraction to the phase containing Trition X-100 surfactant.The surfactant-rich phase was dissolved and diluted by 0.5mL ethanol solution,and scanned from 400nm to 1000nm by ultraviolet-visible spectrophotometer.Under the optimized conditions,linearity was obeyed in the range 0.3—180ng/mL for phosphate.The limit of detection was 0.73ng/mL and relative standard deviation was 2.8%.The method was applied to determination and concentration of orthophosphates in the water samples with satisfactory results.